Increasing Antimicrobial Resistance Profile Diversity of Colonizing Group B Streptococcus in Reproductive-Aged Women...

An increase of group B Streptococcus (GBS) colonization in pregnant women with a parallel rise in neonatal and infant infections, were observed in Korea. We characterized antimicrobial resistance (AMR) and molecular features of GBS isolates from reproductive-aged women between 1994-2000 and 2017-2022.

We collected 246 GBS isolates, 37 during 1994-2000 and 209 during 2017-2022, from cervical and/or anorectal swabs at three institutions. Antimicrobial susceptibility was tested using the MicroScan MicroSTREP Plus Panel (Beckman Coulter, Brea, CA, USA). Sequence types (STs), clonal complexes (CCs), cps genotypes by serotypes, and AMR genes were identified using whole-genome sequencing on the NovaSeq 6000 system (Illumina, San Diego, CA, USA).

During 1994-2000, CC19 was predominant (35.1%, 13/37), whereas during 2017-2022, CC1 became the most common (35.4%, 74/209). cps genotype VIII, previously limited to one ST1 isolate, appeared in 32 ST2 isolates (P =0.037). All isolates remained susceptible to β-lactams and vancomycin. Tetracycline resistance decreased from 97.3% to 60.8% (P <0.001), with tetM prevalence decreasing from 91.7% to 72.4% (P <0.001) and tetO prevalence increasing from 2.8% to 29.9% (P =0.017). Levofloxacin resistance increased from 0% to 23.4% (P =0.001), with 98.0% of resistant isolates carrying both gyrA and parC. The number of resistance profiles increased from six to 16, including 11 newly identified patterns, covering 81.8% of levofloxacin resistant isolates.

The acquisition of diverse resistance genes has expanded AMR profiles in colonized GBS, emphasizing the need for sustained nationwide surveillance.